What do you understand with INTERFACE word?
Till Java
7, Interfaces are quite similar to Classes of java but, you cannot create
instance of an Interface and their
methods are declared without any body.
We know
there are four main features of Object Oriented Language one of them is Abstraction.
Abstraction means
you have only knowledge about methods
signature or say what that method will do but don’t know how it’ll complete
that task for which it is made by programmer.
Example of
Abstraction:
Imagine
you have a method name stepsToGoShoppingMart(); but, you don’t know what are
the steps to go Shopping Mart or you can say you don’t have a specific
knowledge about what are the statements in this method. i.e; Abstraction.
So we can
say Interface is used to achieve
COMPLETE abstraction in java. When
you create an interface it defines what a class can do without saying anything
about how the class will do it.
#Syntax:
interface <nameofyourinterface>
{
//DECLARE
SIGNATURES OF YOUR ABSTRACT METHODS
}
Example of Interface:
interface Finally_got
{
int average_speed=40;
void move();
}
NOTE: Compiler automatically converts methods of Interface as public and abstract, and the data members as public, static and final by default.
Rules for using Interface:
• Methods inside
Interface must not be static, final, and native till java 7 but in java 8 we
can have static methods but only for those methods having complete definition
so that those cannot be overridden.
•
All variables declared inside
interface are implicitly public static final variables (constants).
• All methods declared inside
Java Interfaces are implicitly public and abstract, even if you don't use
public or abstract keyword.
•
Interface can extend one or
more other interface.
•
Interface cannot implement a
class.
•
Interface can be nested inside another interface.
Example of Interface implementation:
interface Finally_got
{
int
average_speed = 40;
void
move();
}
class Vehicle implements Finally_got
{
public
void move()
{
System.out.println("Average speed is "+average_speed);
}
public static void main (String[]
arg)
{
Vehicle
vc = new Vehicle();
vc.move();
}
}
Output is: Average speed is 40
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Co-Author : Bharti Bhati (B.sc. (H) Computer Science)
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